Right-click any webpage and choose Inspect — or press F12. Chrome DevTools opens a panel docked to the browser. Elements tab shows HTML and CSS live. Change styles in the sidebar and see results instantly without editing source files.
Console tab is for JavaScript logs and errors. `console.log` still works; so do breakpoints in the Sources tab. Pause execution, hover variables, step through functions. Network tab lists every request — spot failed APIs, slow images, and 404s in seconds.
The Performance and Lighthouse tabs answer "why is this slow?" Record a page load, see long tasks and layout shifts. Lighthouse scores accessibility, SEO, and best practices — useful before shipping a client site even if you disagree with every suggestion.
Mobile debugging uses device emulation — test responsive layouts without owning every phone. Throttle network to simulate 3G and catch loading pain early. Application tab inspects cookies, local storage, and service workers for PWA work.
Learn keyboard shortcuts: `Ctrl+Shift+C` to pick an element on the page, `Esc` to open the console drawer while on another tab. Pin the tabs you use most; ignore the rest until you need them.
Firefox DevTools and Safari Web Inspector are similar. Skills transfer. DevTools is not just for pros — designers use it to tweak spacing, PMs use it to screenshot network errors for engineers. Five minutes of exploration saves hours of guesswork.